Work trimming mechanisms for sewing machines



w. MAYERAN 2,925,794

WORK TRIMMING MECHANISMS FOR SEWING MACHINES Feb. 23, 1960 Filed April 4, 1958 4 4 9 w. Q l 4 v m a a MW 3 b F 0 2 WE .d

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WITNESS 44mm w United WORK TRIMlVIlNG MECHANISMS FOR SEWING MACHINES William Mayeran, Fairlield, Conn., assignor to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Application April 4, 1958, Serial No. 726,473

3 Claims. (Cl. 112-122) .resilient support for a horizontal trimming blade which will permit the knife to ride over unseverable obstructions in the work.

Another object of this invention is to provide a trimming knife supporting construction of the above character which is compact and free of any projecting parts which might otherwise interfere with work handling on the work supporting post of the sewing machine.

With the above and other objects and advantages in view as will hereinafter appear, this invention is described below with reference to the accompanying drawings of a preferred embodiment in which:

Fig. 1 represents a side elevational view, partly in section, of a portion of a sewing machine bed with a work supporting post and having a work trimming mechanism of this invention applied thereto,

Fig. 2 represents a top plan view of the sewing machine bed and work supporting post of Fig. l, and

Fig. 3 represents an enlarged side elevational view, partly in vertical cross section, of the trimming knife and the supporting arrangement thereof.

Referring to the drawings, 11 denotes a sewing machine bed from which rises a vertical work supporting post 12. A post type of sewing machine is well known in the art and is advantageous in that it provides a small elevated work supporting surface 13 advantageous for sewing tubular or cupped shaped articles where Work manipulation would otherwise be extremely difficult. Provided within the post is a work feeding wheel 14 and a conventional loop taker (not shown) which cooperates with an endwise reciprocatory needle 15 in the formation of stitches. The needle may be supported in a conventional bracket arm (not shown) carried on the machine bed and overhanging the post 12. Also carried on the bracket arm is a driven roller presser 16 which cooperates with the feed wheel 14 to advance work material being stitched.

The present invention relates to a work trimming mechanism of the so-called Barber type, that is, a trimmer employing a horizontally disposed knife blade 20 arranged over the work supporting surface and adapted to be oscillated about a vertical axis. The knife blade is formed with a depending sharpened lip 21 and operates to sever one of a plurality of plies of material adjacent the stitching point on the work support 13.

The work trimming knife blade is carried on and oscillated by a vertical shaft 22 journaled along the work supporting post in bearings 23 thereon. A rock arm 24 tates Patent 2,925,794 Patented Feb. 23, 1960 fast on the shaft 22 is pivotally interconnected by means of a plunger 25 to one arm 26 of a bell crank 27 fulcrumed coaxially with the shaft 22 and formed on its other arm 28 with a bifurcated follower 29 which embraces a block 30 carried on an eccentric pin 31 formed on the free extremity of a rotary knife driving shaft 32. The shaft 32 is journaled in a supporting frame 33 carried on the machine bed and is fitted with a belt pulley 34 and adapted to be driven by a belt 35 from any desired source of power.

Fig. 3 best illustrates the construction by which the knife blade 20 is supported on the shaft 22. A bracket 40 is secured as by a force fit on the upper extremity of the shaft 22. The bracket is formed with an upstanding bracket arm 41 the outer face of which is formed with a vertical channel 42. At the upper extremity, the bracket arm 41 carries a pivot pin 43 for a bell crank lever 44 having a horizontal arm 45 to which the knife blade 20 is secured as by screws 46 accommodated in a slot 47 in the knife blade 20. The second arm 48 of the bell crank lever 44 depends into the channel 42 of the bracket arm 41 and abuts a stop screw 49 threaded through the bracket arm and extending into the channel. Also within the channel and anchored at the lower extremity thereof by a screw 50 is a fiat leaf spring 51 which bears against the tapered outer face 52 of the second arm 48 of the bell crank lever, biasing the bell crank lever in a counterclockwise direction as viewed in Fig. 3 to a position in which the second arm 48 of the bell crank lever abuts the stop screw 49.

This construction thus provides a compact supporting structure for the knife blade which, by virtue of the spring 51, biases the knife cutting edge 21 into proper Work severing position as determined by the positive stop screw 49. Should an unsev'erable obstruction be encountered in the work, the knife blade is free to ride upwardly flexing the spring 51 until the obstruction has passed.

Since the depending arm 48 of the bell crank 44, the stop screw 49, and the spring 51 are all arranged within the channel 42 of the bracket arm 41, the knife support of this invention is free of any projections which might snag or otherwise impede handling of work materials on the work supporting post of the sewing machine.

Having thus set forth the nature of this invention, what I claim herein is:

1. In a sewing machine having a frame formed with a horizontal work supporting surface and stitch forming instrumentalities defining a stitching point on said work supporting surface, a horizontal oscillating work trimming knife member disposed above said work supporting surface, a sharpened cutting edge formed on said knife member, a knife driving shaft, means journaling said knife driving shaft substantially vertically in said sewing machine frame and means for supporting said knife blade on said shaft, comprising a bracket fixed on said shaft, 9. two-armed lever, means pivotally securing said lever on said bracket on a pivotal axis substantially perpendicular to said knife driving shaft, means securing said work trimming knife to a first arm of said lever, stop means carried by said bracket for engagement with a second arm of said lever todetermine an operative position of said work trimming knife, and a spring means anchored on said bracket and bearing upon said second arm of said lever biasing said second lever arm against said stop means.

2. In a sewing machine having a work supporting post and stitch forming instrumentalities defining a stitching point on said work supporting post, a horizontal oscillatory work trimming knife member disposed above said work supporting post, a sharpened knife blade formed on said knife member, a knife driving shaft,

means journaling said knife driving shaft substantially vertically along said work supporting post, and means for supporting said knife blade on said shaft, comprising a bracket fixed on said shaft, an upstanding arm formed on said bracket, a bell crank lever, means pivotally supporting said bell crank lever on said upstanding bracket arm on a pivotal axis substantially perpendicular to said knife driving shaft, means for securing said Work trimming knife member to a first lever arm of said bell crank lever, a second arm of said bell crank lever extending along said upstanding bracket arm, stop means on said bracket for engagement with a second lever arm of said bell crank lever defining an operative position of said bell crank lever With said second lever arm disposed substantially parallel to said upstanding bracket arm, and a leaf spring anchored on said bracket and bearing upon i said bell crank lever biasing said second lever arm against said stop means.

3. A device as set forth in claim 2 in which said upstanding bracket arm is formed with a vertical channel and said stop means, said second bell crank lever arm, and said leaf spring are disposed in said channel.

References Cited in the file of this patent UNITED STATES PATENTS 156,267 Barber Oct. 27, 1874 1,339,742 Corrall et al. May 11, 1920 2,282,200 Neuman May 5, 1942 FOREIGN PATENTS 499,292 Great Britain Jan. 20, 1939 

